1986 Fiscal Year Final Research Report Summary
LASER BEAM DEGRADATION THROUGH TURBULENT SHEAR LAYERS
| Project/Area Number |
60550118
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Fluid engineering
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| Research Institution | TECHNOLOGICAL UNIVERSITY OF NAGAOKA |
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Principal Investigator |
HATTORI HISAO TECHNOLOGICAL UNIVERSITY OF NAGAOKA, Professor, 工学部, 教授 (40134960)
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| Co-Investigator(Kenkyū-buntansha) |
KANEKO SATORU TECHNOLOGICAL UNIVERSITY OF NAGAOKA, Research Associate, 工学部, 助手 (90161174)
MASUDA WATARU TECHNOLOGICAL UNIVERSITY OF NAGAOKA, Associate Professor, 工学部, 助教授 (80143816)
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| Project Period (FY) |
1985 – 1986
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| Keywords | Fluid dynamics / Jet / Turbulent flow / レーザー |
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| Research Abstract |
Aerodynamic windows, which consist of one or more jets of high velocity gas, are frequently used to allow the extraction of laser beams from the laser cavity when the beam power density is sufficiently high to preclude the use of solid windows. The turbulent shear layers at the edges of the jets can produce random phase errors in the laser beam that can substantially reduce the maximum power density to which the beam can be focused. In free vortex aerodynamic windows, the shear layers are curved and the curvature affects the stability of shear layers strongly. However, details of the turbulent structure in the curved shear layers are not well known.
In the present investigation, the structure of a two-dimensional curved jet along a circular arc is measured using the hot wire probes and a split film probe. The following conclusions can be drawn from the experimental results about the curved jet.
1) The profiles of the rms intensity for the axial component of the velocity and the turbulent shear stress exhibit an obvious asymmetry due to the influence of the centrifugal force. On the other hand, the asymmetry in the rms intensity for the lateral component of the velocity is weak.
2) The curvature factor is about 10 in the initial mixing region, decreases rapidly in the downstream direction and approaches a final value of 3 in the self preserving region. The profiles of the turbulent shear stress also show that the curvature factor depends strongly on the laeral direction as well as the downstream direction. The reduction of the mixing in the inner portion of the curved jet due to the centrifugal force is more conspicuous than the enhancement in the outer portion.
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Research Products
(4 results)
